SLK2721

OC48+FEC/24/12/3 SONET/SDH MULTIRATE TRANSCEIVER

WITH ENHANCED JITTER TOLERANCE

SLLS532 − JUNE 2002

11

POST OFFICE BOX 655303

detailed description (continued)

testability

The SLK2721 device has a comprehensive suite of built-in self-tests. The loopback function provides for

at-speed testing of the transmit/receive portions of the circuitry. The ENABLE pin allows for all circuitry to be

disabled so that an IDDQ test can be performed. The PRBS function allows for a built-in self-test (BIST).

IDDQ function

When held low, the ENABLE pin disables all quiescent power in both the analog and digital circuitry. This allows

for IDDQ testing on all power supplies and can also be used to conserve power when the link is inactive.

local loopback

The LLOOP signal pin controls the local loopback. When LLOOP is high, the loopback mode is activated and

the parallel transmit data is selected and presented on the parallel receive data output pins. The parallel transmit

data is also multiplexed and presented on the high-speed serial transmit pins. Local loopback can only be

enabled under transceiver mode.

1:4 Serial to

Parallel

4:1 Parallel to

Serial

RXDATA (3−0)

RXCLK

TXDATA (3−0)

TXCLK

2.488 GHz

PLL

D

D

SRXDIP

SRXDIN

LLOOP

STXDOP

STXDON

Recovered Clock

Figure 3. Local Loopback Data Path

remote loopback

The RLOOP signal pin controls the remote loopback. When RLOOP is high, the serial receive data is selected

and presented on the serial transmit data output pins. The serial received data is also demultiplexed and

presented on the parallel receive data pins. The remote loop can be enabled only when the device is under

transceiver mode. When the device is put under the repeater mode with RX_MONITOR high, it performs the

same function as remote loopback.